CONSOLIDATED STATEMENTS OF EQUITY AND REDEEMABLE NONCONTROLLING INTERESTS - USD ($) $ in Millions	Total	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock	Class B Common Stock Common Stock
Increase (Decrease) in Temporary Equity
Net income	$ 0
BALANCE (shares) at Dec. 31, 2017							76,071,145		25,670,684
BALANCE at Dec. 31, 2017	1,534	$ 1,319	$ 249	$ (1)	$ (34)		$ 1		$ 0
Cumulative effect of adoption of new accounting standard at Dec. 31, 2017	2		2
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(55)		(55)
Repurchases of Class A Common Stock (in shares)							(1,636,019)
Repurchases of Class A Common Stock	(45)	(45)
Class A Common Stock issued pursuant to employee benefit plans (shares)							543,298
Class A Common Stock issued pursuant to employee benefit plans	19	19
Distributions to noncontrolling interests, net	(7)				(7)
Net (loss) income	138		135		3
BALANCE (shares) at Sep. 30, 2018							74,978,424		25,670,684
BALANCE at Sep. 30, 2018	1,586	1,293	331	(1)	(38)		$ 1		$ 0
Increase (Decrease) in Temporary Equity
Net income	0
BALANCE (shares) at Jun. 30, 2018							76,576,980		25,670,684
BALANCE at Jun. 30, 2018	1,585	1,336	285	(1)	(36)		$ 1		$ 0
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(18)		(18)
Repurchases of Class A Common Stock (in shares)							(1,636,019)
Repurchases of Class A Common Stock	(46)	(46)
Class A Common Stock issued pursuant to employee benefit plans (shares)							37,463
Class A Common Stock issued pursuant to employee benefit plans	3	3
Distributions to noncontrolling interests, net	(3)				(3)
Net (loss) income	65		64		1
BALANCE (shares) at Sep. 30, 2018							74,978,424		25,670,684
BALANCE at Sep. 30, 2018	1,586	1,293	331	(1)	(38)		$ 1		$ 0
BALANCE at Dec. 31, 2018	0
Increase (Decrease) in Temporary Equity
Issuance of redeemable subsidiary preferred equity, net of issuance costs	985
Noncontrolling interests acquired in a business combination	380
Distributions to noncontrolling interests, net	(14)
Net income	(11)
BALANCE at Sep. 30, 2019	1,362
BALANCE (shares) at Dec. 31, 2018						68,897,723	68,897,723	25,670,684	25,670,684
BALANCE at Dec. 31, 2018	1,600	1,121	518	(1)	(39)		$ 1		$ 0
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(55)		(55)
Class B Common Stock converted into Class A Common Stock (in shares)							643,002		(643,002)
Class B Common Stock converted into Class A Common Stock	0
Repurchases of Class A Common Stock (in shares)							(3,993,194)
Repurchases of Class A Common Stock	(125)	(125)
Class A Common Stock issued pursuant to employee benefit plans (shares)							1,515,606
Class A Common Stock issued pursuant to employee benefit plans	32	32
Noncontrolling interests acquired in a business combination	231
Distributions to noncontrolling interests, net	(15)				(15)
Net (loss) income	7		4		3
BALANCE (shares) at Sep. 30, 2019						67,063,137	67,063,137	25,027,682	25,027,682
BALANCE at Sep. 30, 2019	1,675	1,028	467	(1)	180		$ 1		$ 0
BALANCE at Jun. 30, 2019	0
Increase (Decrease) in Temporary Equity
Issuance of redeemable subsidiary preferred equity, net of issuance costs	985
Noncontrolling interests acquired in a business combination	380
Distributions to noncontrolling interests, net	(14)
Net income	(11)
BALANCE at Sep. 30, 2019	1,362
BALANCE (shares) at Jun. 30, 2019							67,032,088		25,027,682
BALANCE at Jun. 30, 2019	1,529	1,024	545	(1)	(40)		$ 1		$ 0
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(18)		(18)
Class A Common Stock issued pursuant to employee benefit plans (shares)							31,049
Class A Common Stock issued pursuant to employee benefit plans	4	4
Noncontrolling interests acquired in a business combination	231
Distributions to noncontrolling interests, net	(11)				(11)
Net (loss) income	(60)		(60)		0
BALANCE (shares) at Sep. 30, 2019						67,063,137	67,063,137	25,027,682	25,027,682
BALANCE at Sep. 30, 2019	$ 1,675	$ 1,028	$ 467	$ (1)	$ 180		$ 1		$ 0